Desensitizing dental composition

ABSTRACT

A dental composition for the treatment of dentinal hypersensitivity and in particular for the desensitization of exposed dentin, the desensitizing treatment of deep cavities, the desensitizing treatment when replacing dental layers, the stumps desensitizing treatment before placing dental prosthesis. The composition can be used as a solution or as a gel. In the first case two distinct liquid solutions for use successively on the exposed dentin are provided for. In the second case two distinct gel compounds spread successively on the exposed dentin are provided for. The first solution or the first gel compound comprises preferably three soluble potassium salts, whereas the second solution or the second gel compound comprises a calcium salt and a soluble strontium salt. In a preferred composition two solutions are provided for of which the first has solutes comprising potassium phosphate, potassium carbonate and potassium fluoride, and the second solution has solutes comprising calcium chloride and strontium chloride. For the gel composition, which may be used as toothpaste, two distinct gel compounds are provided, the first having solutes comprising potassium phosphate, potassium carbonate and potassium fluoride and the second gel compound having solutes comprising calcium chloride and strontium chloride.

FIELD OF THE INVENTION

The present invention generally relates to a compound for dentistry and,more precisely, it relates to a dental composition for the treatment ofdentinal hypersensitivity.

In particular, the composition is suitable for the desensitization ofthe exposed dentin, such as, in particular, for

the desensitizing treatment of deep cavities,

the desensitizing treatment when replacing dental layers,

the stumps desensitizing treatment before placing dental prosthesis.

The composition can be used as a solution or as a gel.

DESCRIPTION OF THE PRIOR ART

Dentinal hypersensitivity is a problem often met by dentists in theirpatients and is often intensified when eating hot or cold food, sweet oracidulous food, as well as when brushing teeth.

Normal dentin is covered by enamel (crown dentin) or by cement(radicular dentin) and is not permeable.

In teeth sensitive zones enamel is found often eroded or worn away anddentin exposed. In other cases, gingival recession uncovers the mostsensitive portions of the teeth, i.e. the junction enamel-cement.

The absence of cover exposes the dentinal tubules. In addition, pulp isrich of nerves many of which are centrifugally directed towards dentin.Dentin is crossed radially by dentinal tubules which contain dentinalfluid. Through the tubules a nervous stimulus reaches sensorial areas ofthe dental pulp.

A first known way to reduce dentinal sensitivity is to close theorifices of dentinal tubules. To this extent, natural substances areknown able to reduce sensitivity by closing the tubules, such as tartar,collagen or mineral salts precipitated in saliva.

Chemical compounds, like solutions, gel compounds to or pastes, as wellas physical treatments are also known capable of mechanicallyobliterating the orifices of the dentinal tubules. Compounds of the skind are known in GS2239601 and in WO 92/04006.

Other compounds or treatments or this kind are:

potassium and iron oxalate, which react with ionised calcium present inthe saliva and form calcium oxalate which Precipitates and obliteratesthe dentinal tubules orifices;

silver nitrate which acts through the precipitation of silver compounds;

tin fluoride, which acts through the precipitation of tin compounds;

strontium salts;

insoluble salts such as calcium phosphate, hydroxyapatite, colloidalsilica etc. which directly obliterate the tubular orifices;

glass-ionomeric cement;

some types of resins.

Other compounds, known for example in U.S. Pat. No. 5,603,922 or inWO-A-97/06774, provide a composition useful to remineralize lesions indental enamel. Hypersensitivity is counteracted as a secondary effect,owing to the obliteration of dentin due to remineralization.

In any case the obliteration of the dentinal tubules by means of solubleor insoluble salts used up to now, even if they are simple to use, isnot enough effective and last only a short time.

Compounds are known, moreover, such as potassium chloride or nitrate oroxalate capable of reducing the dentinal sensitivity through adepolarising effect of the nervous fibres, without obliterating thedentinal tubules. Therefore, desensitization treatments are known usingsaid compounds, capable of stopping the pulpal nervous activity byvarying the dentinal tubules nervous fibres excitability. However, alsoin this case, the effect duration is short.

New techniques, not yet used in clinical practice, use glass-ionomericcement or photo-induced resins. Desensitization is improved, but theyare not easy to use and are good for deep erosions only.

Moreover, treatments are known using either laser or ultrasoundsscalers, which cause the formation of smear layers and tubulesobliteration. These treatments give results, such as effectiveness andduration, similar to the topical treatment with the above describedsoluble or insoluble salts, but they require expensive apparatus.

SUMMARY OF THE INVENTION

It is an object of the present invention to provide a dental compositionfor dentinal desensitization which has good mechanical obliterationproperties of the dentinal tubules in addition to depolarisingproperties of the nervous dentinal fibres, arid is capable of obtaininggood effectiveness and long duration, as well as of being easy to use.

According to a first aspect of the invention, this object is reached bythe composition whose characteristic is to comprise at least twosolutions to be used successively on the exposed dentin.

A second aspect of the invention provides at least two distinct gelcompounds to be used successively on the exposed dentin.

The characteristics of said solutions and said gel compounds is tocomprise a first and a second solution or a first and a second gel,suitable for being mixed topically, wherein:

in the first solution a first solute consisting in potassium phosphateand at least a second solute selected among potassium carbonate,potassium fluoride, potassium oxalate, are present, and

in the second solution a first solute selected among a calcium salt andat least a second solute selected among a strontium salt, a silver salt,a barium salt, a zinc salt are present,

whereby a crystal complex is formed comprising

a plurality of insoluble salts having obliterating properties on thedentinal tubules obtained by double exchange reaction of the first andsecond solute of the first and second solution,

a soluble potassium salt having depolarising effect on dentin.

The preferred general weight ratio for the firs solution is thefollowing:

potassium phosphate  0,5-20% potassium carbonate  0,5-10% potassiumfluoride  0,1-5% sodium methylparaben  0,1% deionized water 64,9-98,8%

The preferred general weight ratio for the second solution is thefollowing:

calcium chloride  0,5-20% strontium chloride  0,5-11% benzoate sodium 0,2% deionized water 68,8-98,8%

The preferred general weight ratio for the first gel compound is thefollowing:

potassium phosphate 0,5-10% potassium carbonate 0,5-5% potassiumfluoride 0,1-0,5% sorbitol  30-45% colloidal silica  15-30% glycerol  5-10% carboxy methyl hydroxy ethyl cellulose 0,5-1,5% lauryl sulphatesodium  1.-1,5% benzoate sodium  0,3-0,8% saccharinated sodium  0,3-0,5%mint fragrance q.s. colour CI 42051, CI 19140 q.s. purified water q.s.100 ml

The preferred general weight ratio for the second gel compound is thefollowing:

strontium chloride 0,5-10% calcium chloride 0,5-10% sorbitol  30-45%colloidal silica  15-30% glycerol   5-10% carboxy methyl hydroxy ethylcellulose 0,5-1,5% lauryl sulphate sodium   1-1,5% benzoate sodium0,3-0,8% saccharinated sodium 0,3-0,5% mint fragrance q.s. colour CI16255, CI 47005 q.s. purified water q.s. 100 ml

The combined use of the two preferred solutions or of the two preferredgel compounds successively has the result, after an immediate doubleexchange reaction, of six insoluble salts:

calcium phosphate,

calcium carbonate,

calcium fluoride,

strontium phosphate,

strontium carbonate,

strontium fluoride,

and a soluble salt, i.e. potassium chloride.

According to a sudden reaction a “crystal complex” is formed by said sixinsoluble salts which surprisingly have shown desensitizing propertiesin the short term (15 minutes) and in the long term (6-12 months).

The formation of the potassium chloride helps to increase thedesensitization properties adding a nervous depolarising effect. Infact, potassium chloride is obtained after a double exchange reactionand is present in solution inside the dentinal tubule when the “crystalcomplex” is formed which obliterates the tubules orifices. In this way ahigher amount of potassium is present for a longer time with respect tothe depolarising compounds according to the prior art, which do notobliterate the dentinal tubules, thus allowing the dentinal fluid (whoseflow is always centrifugal) and then also the potassium ions to come outthe dentinal tubules.

The use of an induced crystallisation for obliterating the dentinaltubules with the formation of a “crystal complex” along with theformation (always inside the tubules) of a compound with depolarisingproperties of the nervous fibres, is new in the dental field, and isused with excellent results according to the present invention.

If the composition according to the invention is prepared with potassiumphosphate, potassium carbonate and potassium fluoride (for the firstsolution) in amounts higher than 20, 10 and 5% respectively for thefirst solution and with calcium chloride and strontium chloride inamounts higher than 20 and 11% respectively for the second solution, adesensitizing is obtained having the same good properties as abovedescribed, but less convenient to use. In fact, at the moment of theunion of the two solutions, when the formation of the six insolublesalts occurs, an opalescent gel compound would result, less handy andless spreadable on the surface to cure.

It is also advisable that the two solutions are spread with differentbrushes so that the two solutions or gels are not in contact before theyreach the patient's mouth.

Similarly, the composition with potassium phosphate, potassium carbonateand potassium fluoride in amounts higher than 10, 5 and 0.5% for thefirst gel compound and with calcium chloride and strontium chloride inamounts higher than 10% for both the salts of the second gel compound, adesensitizing composition is obtained which can be used having the sameproperties as above described, but less suitable for a toothpastebecause its organoleptic aspect would be less acceptable.

The composition according to the present invention, will be made clearerwith the not limitative following examples.

EXAMPLE 1.1

A composition for desensitizing exposed dentin which uses two solutionsto be spread successively comprises potassium phosphate, potassiumcarbonate and potassium fluoride for the first solution and calciumchloride and strontium chloride for the second solution, with thefollowing weight ratio:

Solution n° 1 potassium phosphate 16% potassium carbonate  5% potassiumfluoride  3% sodium methylparaben  0.1% deionized water 75,9% Solutionn° 2 calcium chloride 16% strontium chloride 10,6% benzoate sodium  0.2%deionized water 73,2%

The preferred spreading method is the following for the desensitizingtreatment: after having isolated the surgical area with cotton elementsor the like and after having ablated the dental plaque by means of lowspeed electric brushing, the surface to be treated is cleaned by cottonpellets wet by a disinfectant liquid (such as sodium hypochlorite 5%solution). Then the surface is dried with air jet for about 15 seconds.The drying action must substantially dehydrate the external layer of theexposed dentin . Then, by means of a brush or cotton pellets or spongyelements gently rubbed, the first solution is spread for about 20seconds. Immediately after the second solution is spread onto the samedental surface and in the same way.

When hypersensitivity is high, the same treatment can be repeated.

The action of such a composition, which reacts forming a crystal complexwhich deeply obliterates the dentinal tubules orifices is double. Infact, the first solution spread on the dehydrated dentin causes, forcapillarity, the filling of the dentinal tubules. To this the nervousdepolarisation is added of the potassium chloride which always formsinside the tubules through a double exchange reaction.

Alternatively to the composition of the above example 1, in the same waythe following exemplifying compositions can be used. In thesecompositions only two potassium salts are present in the first solutionand the crystal complex will be formed by 4 insoluble salts only.Soluble potassium salts are still present.

EXAMPLE 1.2

Solution n° 1 potassium phosphate 16% potassium oxalate  6% sodiummethylparaben 0.1%  deionized water q.s. 100 ml Solution n° 2 calciumchloride 16% strontium chloride 10% benzoate sodium 0.2%  deionizedwater 73,8%  

EXAMPLE 1.3

Solution n° 1 potassium phosphate 16% potassium carbonate  5% sodiummethylparaben 0.1%  deionized water q.s. 100 ml Solution n° 2 calciumchloride 16% barium chloride 10% benzoate sodium 0.2%  deionized water73,8%  

EXAMPLE 1.4

Solution n° 1 potassium phosphate 16% potassium carbonate  5% sodiummethylparaben 0.1%  deionized water q.s. 100 ml Solution n° 2 calciumchloride 16% silver chloride 10% benzoate sodium 0.2%  deionized water73,8%  

EXAMPLE 1.5

Solution n° 1 potassium phosphate 16% potassium carbonate  5% sodiummethylparaben 0.1%  deionized water q.s. 100 ml Solution n° 2 calciumchloride 16% zinc chloride 10% benzoate sodium 0.2%  deionized water73,8%  

EXAMPLE 1.6

Solution n° 1 potassium phosphate 16% potassium carbonate  5% sodiummethylparaben 0.1%  deionized water 78,9%   Solution n° 2 calciumchloride 16% strontium chloride 10,6%   benzoate sodium 0.2%  deionizedwater 73,2%  

EXAMPLE 2

A desensitizing composition to be used as a toothpaste which usessequentially two gel compounds comprising potassium phosphate, potassiumcarbonate and potassium fluoride for the first gel compound and calciumchloride and strontium chloride for the second gel compound, with thefollowing weight ratio:

Gel compound n° 1 potassium phosphate   8% potassium carbonate 3,5%potassium fluoride 0,4% sorbitol  30% colloidal silica  15% glycerol  5% lauryl sulphate sodium 1,5% carboxy methyl hydroxy ethyl cellulose  1% benzoate sodium 0,5% saccharinated sodium 0,4% mint fragrance q.s.colour CI 42051, CI 19140 q.s. purified water q.s. 100 ml Gel compoundn° 2 calcium chloride   7% strontium chloride   6% sorbitol  30%colloidal silica  15% glycerol   5% lauryl sulphate sodium 1,5% carboxymethyl hydroxy ethyl cellulose   1% benzoate sodium 0,5% saccharinatedsodium 0,4% mint fragrance q.s. colour CI 16255, CI 47005 q.s. purifiedwater q.s. 100 ml

This composition is used in the following way for the desensitizingtreatment:

on the toothbrush an amount of gel compound n°1 substantially equal tothe volume of two peas is poured;

both dental arches are spread with gel compound n°1 by brushing from theabove to the bottom for about two minutes;

the friction is prolonged on the areas which are sensitive to hot orcold food, to acidulous or sweet substances;

without rinsing, after having spread on the toothbrush the same amountof gel compound n°2, the same dental surface is brushed again as abovedescribed for the first gel compound;

after the two gel compounds have mixed on the dental surface an instantdouble exchange reaction occurs with the formation of the “crystalcomplex”, comprising the six insoluble salts and potassium chloride;

then the mouth is rinsed with water.

The foregoing description of specific embodiments will so fully revealthe invention according to the conceptual point of view, so that others,by applying current knowledge, will be able to modify and/or adapt forvarious applications such embodiments without further research andwithout departing from the invention, and it is therefore to beunderstood that such adaptations and modifications will have to beconsidered as equivalent to the specific embodiments. The means and thematerials to realise the different functions described herein could havea different nature without, for this reason, departing from the field ofthe invention. It is to be understood that the phraseology orterminology employed herein is for the purpose of description and not oflimitation.

What is claimed is:
 1. A method for depolarizing dentin and obliteratingdentinal tubule orifices of a subject with hypersensitive dentin, whichcomprises the steps of: providing a first liquid solution or gelcomprising potassium phosphate as a first solute and at least a secondsolute comprising one other potassium salt selected from the groupconsisting of potassium carbonate, potassium fluoride and potassiumoxalate; providing a second liquid solution or gel comprising a calciumsalt as a first solute and at least a second solute selected from thegroup consisting of a salt of strontium, silver, barium and zinc;topically applying said first and second liquid solutions or gels to thedentinal tubule orifices in the dentin of a subject with hypersensitivedentin in need of dentinal depolarization and obliteration of dentaltubules, and mixing topically on said dentinal tubule orifices on saidhypersensitive dentin to form a dental desensitizing compositioncomprising the first and second solutions or gels to generate a crystalcomplex inside the dental tubules comprising a plurality of insolublesalts obtained by double exchange reaction of said salts, and furthersoluble potassium salt, wherein said insoluble salts have anobliterating effect on the dentinal tubules, said soluble potassium salthaving a depolarizing effect on said dentin.
 2. The method according toclaim 1, wherein the first solute in said second liquid solution is amember selected from the group consisting of calcium chloride andcalcium acetate, and the second solute is a member selected from thegroup consisting of strontium chloride, strontium acetate, silverchloride, barium chloride and zinc chloride.
 3. The method o accordingto claim 1, wherein said first solute in said second gel is calciumchloride and the second solute is strontium chloride.
 4. The methodaccording to claim 1, wherein said first and second liquid solutions orgels comprise a solvent and a bacteriostatic preservative.
 5. The methodaccording to claim 4 wherein the solutes of the first solution arepotassium phosphate, potassium carbonate and potassium fluoride; and thesolutes for the second solution are calcium chloride and strontiumchloride, and are present in the following general weight ratio:Solution no. 1 potassium phosphate  0,5-20% potassium carbonate  0,5-10%potassium fluoride  0.5-5% Preservative  0.1% Solvent 64.9-98.4%Solution no. 2 calcium chloride  0.5-20% strontium chloride  0.5-10%Preservative ‘0.2% Solvent 69.8-98.8%


6. The method according to claim 5 wherein said solvent is deionizedwater and said preservative is sodium methylparaben for said solutionno. 1 and benzoate sodium for said solution no.
 2. 7. The methodaccording to claim 6 wherein said solutes, solvent, and preservative arepresent in the following weight ratio: Solution no. 1 potassiumphosphate  16% potassium carbonate   5% potassium fluoride   3% sodiummethylparaben 0.1% deionized water 75.9%  Solution no. 2 calciumchloride  15% strontium chloride 10.6%  benzoate sodium 0.2% deionizedwater 74,2%  Preservative 0.2% Solvent 69.8-98.8%


8. The method according to claim 4, wherein in said first liquidsolution, said at least second solute is potassium oxalate; and in saidsecond liquid solution the first solute is a member selected from thegroup consisting of calcium chloride and acetate and the second soluteis selected from the group consisting of strontium chloride, strontiumacetate, silver chloride, barium chloride and zinc chloride, and saidsolvent is deionized water and said preservative is sodium methylparabenfor the first solution and benzoate sodium for the second solution. 9.The method according to claim 3 for use as gel toothpaste suitable fordesensitizing exposed dentin, wherein the solutes for the first gel arepotassium phosphate, potassium carbonate and potassium fluoride and thesolutes for the second gel are calcium chloride and strontium chlorideand the other compounds are present according to the following generalweight ratio: Gel compound no. 1 potassium phosphate 0.5-10%  potassiumcarbonate 0.5-5%   potassium fluoride 0.1-0.5% sorbitol 30-45% colloidalsilica 15-30% glycerol  5-10% carboxy methyl hydroxy ethyl cellulose0.5-1.5% lauryl sulphate sodium   1-1.5% benzoate sodium 0.3-0.8%saccharinated sodium 0.3-0.5% mint fraqrance qs. colour CI 42051, CI19140 qs. purified water qs. 100 ml Gel compound no. 2 strontiumchloride 0.5-10%  calcium chloride 0.5-10%  sorbitol 30-45% colloidalsilica 15-30% glycerol  5-10% carboxy methyl hydroxy ethyl cellulose0.5-1.5% lauryl sulphate sodium   1-1.5% benzoate sodium 0.3-0.8%saccharinated sodium 0.3-0.5% mint fragrance qs. colour CI 16255, CI47005 qs. purified water qs. 100 ml


10. The method according to claim 8 wherein said solutes and the othercompounds are present in the following weight ratio: Gel compound no. 1potassium phosphate   8% potassium carbonate 3.5% potassium fluoride0.4% sorbitol  30% colloidal silica  15% qlycerol   5% lauryl sulphatesodium 1.5% carboxy methyl hydroxy ethyl cellulose   1% benzoate sodium0.5% saccharinated sodium 0.4% mint fragrance qs. colour CI 42051, CI19140 qs. purified water qs. 100 ml Gel compound no.2 calcium chloride  7% strontium chloride   6% sorbitol  30% colloidal silica  15%glycerol   5% lauryl sulphate sodium 1.5% carboxy methyl hydroxy ethylcellulose   1% benzoate sodium 0.5% saccharinated sodium 0.4% mintfragrance qs. colour CI 16255, CI 47005 qs. purified water qs. 100 ml